Mechanical stress changes the electronic parameters of micro-electronic devices. Circuits that depend on these parameters or absolute values thereof, such as Hall sensors, constant current sources and band-gap regulated reference voltages, can suffer from a stress drift. The drift of these circuits can be reduced by measuring the mechanical stress and compensating the resulting drift for this measured stress change.
Stress sensors can be made by comparing two different diffused or implanted resistors, such as a lateral p-type resistor with a lateral n-type resistor or a lateral n-type resistor with a vertical n-type resistor. The former can suffer from different temperature coefficients between p- and n-type resistances. While the latter has much better matching of temperature coefficients, there is still a notable difference in these coefficients between vertical and lateral n-type resistances. In practice, different n-wells for lateral and vertical resistors are typically used in CMOS technology such that the temperature coefficient, which depends on the doping level, is not identical. Additionally, a significant technology spread between different doping levels usually has to be contended with.